Recognising common short forms of appliances used daily
This is a pretty broad topic!

The question you're interested in has several parts.

The first part is Named Entity Recognition. This NLP task focuses on identifying the types of named objects. In your case, you'd want to be able to tell that something is an appliance (or perhaps even, that it is an air conditioner).

But that's not enough on its own. You also need to be able to tell which appliance they're talking about! This is usually studied as a separate problem, called Entity Recognition.

Both of these are considered pretty hard, and there isn't likely to be one "right" answer for your specific problem, but there are viable techniques. The wikipedia articles I linked to should be good starting places and suggest some out-of-the-box toolkits.